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  • Author or Editor: Carl A. Bradley x
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Poor crop establishment is a major problem in edamame (Glycine max), a specialty type of soybean produced in locations throughout the United States. The objective of this research was to quantify the extent to which seed treatment with fludioxonil + mefenoxam improves seedling emergence of edamame. Emergence characteristics of fludioxonil + mefenoxam-treated and nontreated seed of 30 cultivars were characterized in field conditions over 2 years. Edamame cultivars used in the study exhibited poor field emergence in a previous study despite high germinability. Seed treatment with fludioxonil + mefenoxam at 2.5 and 3.75 g/100 kg seed, respectively, improved crop emergence 33% to 47% more than the nontreated control. The emergence rate (days to 50% emergence) was improved the most by the seed treatment for several cultivars that were generally slow to emerge. Crop establishment is essential for further development of domestic edamame production. Seed treatment with fludioxonil + mefenoxam, at the rate currently registered for use on grain-type soybean, offers one approach to help vegetable growers improve edamame seedling emergence.

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A chickpea (Cicer arietinum) seedlot, naturally infected with Ascochyta rabiei, was sorted into two lots of asymptomatic and symptomatic, based on visual symptoms observed. A laboratory assay showed 16% A. rabiei infection in asymptomatic seeds, while symptomatic seeds had 73% infection. Asymptomatic and symptomatic seeds were treated with different fungicides to determine their effects on seedling emergence from soil and on ascochyta blight development in seedlings grown in a growth chamber and in the field at Fargo and Carrington, ND, in 2006. The emergence of seedlings grown from asymptomatic seeds was significantly (P ≤ 0.05) greater than the emergence of seedlings grown from symptomatic seeds in the growth chamber and field trials. Fungicides were able to increase plant emergence from symptomatic seeds when compared with a control in the growth chamber trials. In the growth chamber trials, the treatment with a mixture of metalaxyl + thiabendazole + ipconazole + azoxystrobin was the most effective at slowing the development of disease on plants from symptomatic seeds. This research reinforces the importance of seed health testing and fungicide seed treatments as part of an ascochyta blight management program.

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Recently, claims have been made that the use of glyphosate and transgenic crop traits increases plant susceptibility to pathogens. Transgenic traits used widely for years in dent corn are now available in commercial sweet corn cultivars, specifically, the combination of glyphosate resistance (GR) and Lepidoptera control (Bt). The objective was to assess the interactions of the GR+Bt trait, glyphosate, and Goss’s wilt on sweet corn. Nine treatments were tested under weed-free conditions at two sites in 2013 and 2014. Treatments included two isogenic cultivars differing only in the presence or absence of GR+Bt, with and without postemergence application of glyphosate, and inoculation with the causal agent of Goss’s wilt (Clavibacter michiganensis ssp. nebraskensis) before glyphosate application, after glyphosate application, or no inoculation. Results failed to show glyphosate or the GR+Bt trait influenced sweet corn susceptibility to Goss’s wilt. The only factor affecting Goss’s wilt incidence was whether plants were inoculated with C. michiganensis ssp. nebraskensis. In the absence of glyphosate application, yet under weed-free conditions, several yield traits were higher in sweet corn with the GR+Bt trait. Results showed that the GR transgene confers the same level of tolerance to glyphosate in sweet corn as observed previously in dent corn. If true, recent claims about glyphosate and transgenic traits increasing plant disease would be of major concern in sweet corn; however, no relationships were found between the GR+Bt trait and/or glyphosate to Goss’s wilt incidence in sweet corn.

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